Background: In prostate cancer, mutations of the phosphatase PTEN can activate the kinase cascade PI3K/Akt/mTOR which induces drug resistance.
Methods: Chemosensitization by siRNA targeting Akt was studied in HEK293 cells forced to express CA-Akt or kinase-dead DN-Akt. To decrease drug resistance, Akt was silenced with siRNA in human prostate DU-145 cell line expressing the normal PTEN or in LNCaP and PC3 cell lines expressing mutated-PTEN. Taxol was used for the chemosensitization studies.
Results: Silencing Akt in the drug-resistant CA-Akt cells efficiently sensitized cells to antitubule agents, whereas silencing drug-responsive DN-Akt cells did not. Only minor effects were obtained in wild-type HEK293 cells. Potentiation by siRNA of taxol cytotoxicity was significantly greater in mutated-PTEN cells than in prostate cells expressing wild-type PTEN. The apoptotic program induced by taxol was preferentially potentiated by Akt siRNA in PTEN-mutated cell lines as regards the DU-145 cell line.
Conclusions: Silencing Akt in PTEN-mutated prostate cancer cells enhances the antitumor effects of taxol. No siRNA chemosensitization was obtained in prostate cells with wild type PTEN.
(c) 2007 Wiley-Liss, Inc.